Cryosurgical probes are used to treat a variety of diseases. The cryosurgical probes quickly freeze diseased body tissue, causing the tissue to die after which it will be absorbed by the body or expelled by the body. Cryothermal treatment is currently used to treat prostate cancer and benign prostate disease, breast tumors and breast cancer, liver tumors and cancer, glaucoma and other eye diseases. Cryosurgery is also proposed for the treatment of a number of other diseases.
The use of cryosurgical probes for cryoablation of the uterus is described in Cahan, W. G. and Brockunier, A., Cryosurgery of the Uterine Cavity. Am. Obstet. Gynec. 99:138-153, 1967. Cahan and Brockunier describe a cryosurgical probe patterned after the curve and diameter of a No. 6 Hegar dilator. Liquid nitrogen circulates through this cryosurgical probe in order to cause cryonecrosis of the diseased endometrial tissue in the uterus. Multiple applications of freezing and thawing are applied using the curved probe in order to treat left and right cornu of the uterus as well as the fundus. This method of cryosurgery has a number of drawbacks because the uterus has, for example, an irregular shape resulting from the left and right cornu. Moreover, the uterus has a rough and irregular lining which is not amenable to efficient cryosurgery. Because of the irregular shape and rough lining of the uterus, a clinician will often miss a portion of diseased tissue and must subject the patient to multiple sessions of cryosurgery. In addition, should the cryoprobe perforate the uterus, life-threatening or fatal hemorrhage may result because of the highly vascular nature of the uterine lining.
Precise positioning of the cryoprobe is thus vital to prevent perforation or unnecessary multiple sessions of cryosurgery. Typically, a clinician monitors the position of the cyroprobe within the uterus by using an ultrasound probe inserted in the rectum or through an external ultrasound transducer. Alternatively, the clinician may monitor the position of the cryoprobe through imaging with x-rays. Monitoring the position of the cyroprobe with such means, however, suffers from a number of drawbacks. For example, a clinician examining ultrasound and x-ray images will have difficulty in distinguishing uterine tissue from the surrounding organs. The clinician would much prefer positioning the cryoprobe under direct vision rather than using such indirect means. There is a need in the art for better techniques in positioning a cryoprobe before ablation. Other ablation devices such as microwave ablation needles also require precise positioning. The present invention addresses this need in the art.